The TUC has voted to support co-ordinated strike action over a public sector pay freeze. It comes after Unison and the GMB union said they were planning the logistics of strike action if annual talks with ministers on government pay fail. The National Union of Teachers and the NASUWT teaching union have also backed a rolling programme of action in England and Wales.

What is the background to the action?

Unions are angry at changes proposed by the government to public sector pensions. These would result in workers having to:

pay more into their pension

work for longer

and accept a pension based on a "career average" salary, rather than the current final salary arrangement which many of them are currently on

The unions complain that the changes will basically leave public sector staff paying more and working longer for less.

Who took part in previous strikes?

Unions involved in strike action in May included:

the Public and Commercial Services Union (PCS), the largest civil service trade union whose members include job centre, border and tax office staff

the University and College Union, comprising lecturers and other staff in colleges and new universities

the Rail, Maritime and Transport union's sailors in the Royal Fleet Auxiliary

the Northern Ireland Public Services Alliance

The Immigration Services Union, which represents 4,500 Border Force staff, also joined the strike. It is protesting specifically against the raising of the retirement age beyond 65, saying the physical demands of the job mean its members should not work into their late 60s.

Was anyone else involved in protests?

On the same day, rank-and-file police officers staged a march in London in protest at budget cuts and proposals for the most wide-ranging reform of pay, pensions and conditions for police in England and Wales in more than 30 years.

Police are currently banned by law from taking industrial action, so thousands of off-duty officers joined the rally.

Why is the government proposing changes?

It wants to save billions of pounds from its public pensions bill.

The government says it is committed to ensuring that public sector pensions "are affordable, sustainable, high quality and fair in the face of huge demographic changes" - primarily that people are living for longer.

The Office for Budget Responsibility (OBR) has predicted that the cost to the taxpayer of providing public sector pensions will more than double to £9bn by 2014/15.

The government argues that, at a time when private sector final salary schemes have been closed and returns from defined contribution schemes are falling, "unreformed gold-plated" public sector pensions are unfair and unaffordable.

What does the government think needs to be done?

It wants to phase in substantial increases in employee contributions to public sector pensions between now and 2015.

It is also planning to bring in new - and less generous - career average pension schemes for most public sector employees.

And it wants public sector workers - bar the armed forces, police and fire service - to receive their occupational pension at the same time as the state pension age, which will eventually rise to 68. Many can currently receive a full pension at 60.

The government maintains that public sector workers will continue to get a good pension, and that low- and middle-income staff who retire after a full career will do as well as, or even better than, under current arrangements.

What do the unions say?

As well as complaining about an attack on their pensions, for which members will have to pay more, the trade unions have accused the government of failing to engage in genuine negotiations towards a settlement.

They have also argued that public sector workers should not be targeted in order to reduce a public deficit they did not cause. And the unions have highlighted the pay freeze currently faced by public sector workers at a time of high inflation, resulting in declining living standards.

Don't public sector workers get paid less because their pensions are better?

This is a myth, according to Lord Hutton. The former Labour work and pensions secretary was commissioned to investigate public service pensions, and many of the government's plans stem from his recommendations.

He found "no evidence that pay is lower for public sector workers to reflect higher levels of pension provision". Although 85% of public service employees contribute to a pension, he said that these pensions were far from "gold-plated", with the average pension in payment currently at a "modest" £7,800 a year. About half of public service pensioners received less than £5,600 a year.

In the private sector only 35% of workers sign up for a pension.

Has the government changed its offer at any point?

Yes. An enhanced offer was made by the government late last year, which included more generous accrual rates (the rate at which a pension builds up), higher "cost ceilings" on taxpayer contributions and transitional protection for workers close to retirement age. On the back of those concessions, some unions signed up to a set of points for further discussions.

At the end of those talks, in March this year, the government published what it called its proposed final agreements. Chief Secretary to the Treasury Danny Alexander said they would mean public servants "rightly continue to receive pensions that are among the very best available, while delivering the government's key objectives in full".